Hamburg, Germany - St. John's Wort can be as good at lifting depression as pharmaceutical drugs such as Prozac, according to German researchers.

A review of research evidence concluded that the herbal extract was as effective as standard antidepressants, but had fewer side effects.

Scientists pooled data from 29 studies involving 5,489 patients with mild to moderately severe depression.

The studies compared the effects of the plant Hypericum perforatum - popularly known as St John's Wort - with inactive "dummy" placebos or a wide range of old and new antidepressants, including Selective Seretonin Re-uptake Inhibitors (SSRIs) such as Prozac and Seroxat.

"Overall, the St. John's Wort extracts tested in the trials were superior to placebo, similarly effective as standard antidepressants, and had fewer side effects than standard antidepressants," the researchers led by Dr Klaus Linde, from the Centre for Complementary Medicine in Munich, Germany, reported.

However, they warned that some smaller German studies may have produced over-optimistic results.

They added that St. John's Wort products available in health food shops and chemists differed greatly and some may be more effective than others.

"Using a St. John's Wort extract might be justified, but products on the market vary considerably, so these results only apply to the preparations tested," said Dr Linde.

The findings were published by the Cochrane Library, which specialises in systematic reviews of research studies.